This application claims the priority of German Patent Document 100 08 130.4, filed Feb. 22, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an apparatus of a spinning machine for the drafting and subsequent condensing of a fiber strand, comprising a condensing zone located downstream of a front roller pair of a drafting unit, an air-permeable transport belt which transports the fiber strand through the condensing zone, a suction channel arranged at the condensing zone, which suction channel guides the transport belt over a sliding surface, a suction slit arranged in the sliding surface, a nipping roller which drives the transport belt and presses the fiber strand and the transport belt to the sliding surface at the end of the condensing zone, a top weighting arm of the drafting unit which top weighting arm supports the nipping roller and a front pressure roller of the front roller pair, and a drive belt which connects the front pressure roller with the nipping roller.
Important for the condensing of a fiber strand leaving a drafting unit is that the fiber strand is transported in the condensing zone disposed on an air-permeable transport element and still in a twist-free state and having fibers which lie essentially parallel to one another, and that in the condensing zone an air stream is generated which flows through the transport element, which air stream determines or assists the degree of condensing depending on its width and/or direction and which assists positioning of the fibers transversely to the transport direction so that the fiber strand is bundled or condensed. In the case of a fiber strand condensed in this way, a spinning triangle does not occur, so that the arising thread is more even, tear resistant and less hairy.
In the case of an apparatus of the above mentioned type (U.S. Pat. No. 6,108,873), the transport element is an air-permeable transport belt, which is driven by the nipping roller. A transfer belt (not described in detail) is provided as a drive belt for the nipping roller. The way in which the necessary tensioning of the drive belt is effected is left open here.
It is an object of the present invention to create for the apparatus of the above mentioned type, a suitable device comprising a drive belt for the nipping roller.
This object has been achieved in accordance with the present invention in that the nipping roller and the front pressure roller are arranged on holding arms which can be spread apart and which tension the drive belt.
Two holding arms are preferably provided for the nipping roller and the front pressure roller, which are joined together via a hinge joint, against which a weighting spring is pressed. By means thereof, the front pressure roller and the nipping roller can move apart when loaded and thus tension the drive belt.
If the drive belt is a toothed belt, not only does a clear ratio between the circumferential speeds of the nipping roller and the front pressure roller exist, but also in the case of the nipping roller jamming due to thread windings occuring, the toothed belt can skip over teeth on the drive wheels, so that, for example, a flexible coating of the nipping roller is not abraded.
The drive belt can be provided with a predetermined breaking point, so that the drive belt tears if the nipping roller jams.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.